A fluidized-bed device can perform granulation coating and drying of pharmaceuticals, food or the like within a single device and has an airtight structure, so that it is a suitable device in view of GMP. Therefore, granulation substances obtained by using this have characteristics of comparatively porous and amorphous shapes and good solubility, and so are widely utilized.
While there are many kinds of fluidized-bed devices (for example, “Granulation Handbook”, edited by The Association of Powder Process Industry and Engineering, Japan, published from Ohmsha, pp.283–348), the devices are roughly divided into a batch type and a continuous type (including a semi-continuous type and a continuous type) as methods of operation.
Presently, in most cases of performing granulation for pharmaceuticals or the like, the batch type of the device is utilized. This is because the batch type thereof is more suitable for obtaining uniform granulation substances in particle size, and is superior in view of GMP since satisfactory dry products can be obtained within the same device and no generated particles need to be transferred to another drying device.
In contrast thereto, in the continuous type as illustrated, for example, in FIG. 7.56 of page 301 and FIG. 7.57 of page 302 in the “Granulation Handbook”, raw materials are continuously injected and granulation substances classified by a principle of pneumatic classification or the like are continuously discharged. This does not need independent steps preceding and following a main step of raw material injection, preliminary mixing, heating, cooling, discharging or the like, and therefore the processing time thereof is shortened. Control and management of the step can be also facilitated since performing stationary operations becomes possible theoretically.
However, since particles of all stages of a granulation process are included in a fluidized-bed obtained by using the continuous type thereof, the particles are classified by the pneumatic classification and are discharged and so there are such drawbacks that classification effect is difficult to expect entirely and a particle size distribution of products to be discharged becomes large, and that products to be dried completely are not obtained since the granulation substances are discharged from a fluidizing chamber in which binder liquids are continuously sprayed, and the like.
Suggestions have been made for improving these drawbacks. For example, the device disclosed in Japanese Patent Laid-open No. 62-282629 is provided with a drying chamber adjacent to a granulation chamber, but the drying chamber has a drying effect and contributes to no improvement in a particle size distribution. Also, the devices described in FIG. 7.59 and FIG. 7.61 of page 303 of the “Granulation Handbook” are each provided with a classifier to keep particle sizes uniform. However, these devices are each suggested as a system and they themselves are not necessarily improved. Therefore, non-uniformity of particle sizes of the products obtained by the continuous type remains fatefully without being improved.
Also, since the batch type of the device intermittently performs injection and discharge, an operating property of the semi-continuous type has an intermediate property of those of the batch type and the continuous type and the semi-continuous type is a type more similar to either one regarding the relation between an injection and discharge amount and a process amount (a retention amount). Therefore, a merit and demerit of the semi-continuous type has an intermediate property of those of both types.
To compensate for such a demerit of the continuous type as described above, the device of a batch type is used in granulation, coating and the like of pharmaceuticals. However, the device has a problem of scaling up the fluidized-bed device as the production thereof is scaled up.
More particularly, upsizing the device causes extensions of the time required for a batch in comparison to a small-sized device, so that the production capacity per unit time does not become proportional to a charge amount but will be below the charge amount. This is because while the amount of charge increases in proportion to a device size to the third power, an amount of fluidizing gas for maintaining an optimal fluidized condition is proportional to the device size to the second power (cross section area) and a drying speed of contents is proportional to the amount of fluidizing gas and so the time required for the drying increases in proportion to the device size.
In a large-sized device, a bulk density of the granulated particles becomes large and thereby the above-mentioned advantages of the fluidized-bed granulation substances are reduced. It is thought that this is because the particles continuously repeat movements of dropping to a bottom portion thereof even during fluidization and thereby weight of the particles in being temporally deposited becomes larger than that of a small-sized device.
Even from the viewpoint of operation, the larger the device becomes, the more difficult maintaining a good fluidizing condition becomes and faulty fluidizing conditions such as channeling, bubbling, slagging or the like are likely to occur.
As described above, since it is not favorable to upsize the fluidized-bed device to a more degree than a certain degree, small-sized devices with used experience are arranged in parallel and the same granulating processes is performed by at least two of the small-sized devices.
However, in this method, it is likely that there will arise problems of no improvement in a floor area for setting the devices and/or in production efficiency per worker as the production scale is increased, and of being unable to enjoy merits of mass production, and further of non-uniform quality of the granulation substances owing to unevenness of respective operating conditions between the devices. This is because there is also the fact that, in the fluidized-beds, the number of operating conditions is large in comparison with other granulating methods and this method is more easily developed than other methods owing to an influence of the unevenness.
Therefore, the present inventors have considered that a continuous type device, which takes an advantage of the merits of a batch type device and improves producing capability per floor area, must be developed.
An object of the present invention is to provide a fluidized-bed granulation coating device such that the handling based on each of the steps constituting a fluidized-bed granulation coating process is vertically constituted as a batch method and thereby each of the steps constituted as such a batch method is processed continuously.
An object of the present invention is to provide a fluidized-bed granulation coating method, such that the handling based on each of the steps constituting a fluidized-bed granulation coating process is continuously done upward to downward.